Standing on Apollo’s Shoulders: A Microseismometer for the Moon
Ceri Nunn, W. T. Pike, I. M. Standley, S. B. Calcutt, S. Kedar, M. P. Panning
Abstract
Abstract Seismometers deployed on the Moon by the Apollo astronauts from 1969 to 1972 detected moonquakes and impacts, and added to our understanding of the lunar interior. Several lunar missions are currently being planned, including the Commercial Lunar Payload Services (CLPS), the Lunar Geophysical Network, and the astronaut program Artemis. We propose a microseismometer for the Moon: the Silicon Seismic Package (SSP). The SSP’s sensors are etched in silicon, and are predicted to have a noise floor below <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>2</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>10</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:mo stretchy="false">(</mml:mo> <mml:mi mathvariant="normal">m</mml:mi> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">)</mml:mo> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msqrt> <mml:mrow> <mml:mi>Hz</mml:mi> </mml:mrow> </mml:msqrt> </mml:math> between 0.3 and 3 Hz (similar to the Apollo instruments between 0.3 and 0.5 Hz, and better than Apollo above 0.5 Hz). The SSP will measure horizontal and vertical motion with the three sensors in a triaxial configuration. The instrument is robust to high shock and vibration and has an operational range from −80°C to +60°C, allowing deployment under harsh conditions. The first-generation version of this sensor, the SEIS-SP, was deployed on Mars in 2018 as part of the InSight mission’s seismic package. We will reconfigure the seismometer for the lower gravity of the Moon. We estimate that a single SSP instrument operating for one year would detect around 74 events above a signal-to-noise ratio of 2.5, as well as an additional 500+ above the noise floor. A mission lasting from lunar dawn until dusk, carried on a CLPS lander, could test the instrument in situ, and provide invaluable information for an extensive future network.